When a handset is brought into proximity to a reflector, e.g. a tabletop or hand, the near field of the antenna is disrupted. This disruption changes the impedance of the antenna and thus changes the output load impedance of the power amplifier (PA). Since the power amplifier efficiency, linearity and harmonic performance are functions of load impedance, when the antenna is mismatched, the transmitter loses efficiency and distorts the output signal. The power efficiency loss results in less talk time but can be mitigated with a larger battery. As the handset must meet strict government regulations regarding distortion, the power amplifier must handle the changing load impedance without exceeding the allowed distortion.
One prior art technique is to supply the power amplifier (PA) with significantly more primary power. This allows for more linear operation into mismatch, but results in an inefficient, large power amplifier. This reduces the talk time unless the battery is grown, and increases the cost of the PA. Another prior art technique uses two smaller PAs. The load to each PA is inverse to one another. Thus, when one sees an open, the other sees a short. This minimizes distortion but requires more semiconductor area. The efficiency suffers due to the loss in the combined network. Alternatively, an isolator may be placed between the power amplifier and the antenna. The isolator adds cost, is large, adds loss and so requires a larger PA, and restricts the bandwidth of the transmitter.